RESEARCH WORK

Performance of 23 Leucaena spp. accessions under establishment conditions

Hilda B. Wencomo¹ y R. Ortiz²

E-mail: hilda.wencomo@indio.atenas.inf.cu

²Instituto Nacional de Ciencias Agrícolas, La Habana, Cuba

ABSTRACT

Twenty-three Leucaena spp. accessions from a collection of 180 were evaluated, with the objective of learning their performance under establishment conditions and select the most outstanding ones, based on some morphological and yield indicators. The plants were sown at a distance of 6 x 3 m between rows and plants. The evaluated indicators were: plant height, number of branches, stem diameter and yield. L. leucocephala CIAT-17480, CIAT-9438, CIAT-7988, CIAT-7384 and CIAT-751, as well as L. esculenta CIAT-17225 and CIAT-17229 were the first ones to reach the height and stem diameter according to the established selection criteria. It could be observed that the establishment dynamics of the species from this genus showed differences among the accessions; likewise, it was noticed that all of them fulfilled the selection criteria, although not at the same time. It is concluded that there are intraspecific and interspecific differences in the evaluated material. The most outstanding accessions were L. leucocephala cv. Cunningham, cv. Peru, CIAT-9119, CIAT-9438, CIAT-751, CIAT-7988, CIAT-7384, CIAT-7929, CIAT-17480, cv. Ipil-pil, cv. CNIA-250, L. lanceolata CIAT-17255, CIAT-17501 and L. diversifolia CIAT-17270, for which their utilization in further studies is recommended.

Key words: Leucaena spp., plant establishment, selection

INTRODUCTION

Many works have reported that legumes, in general, show serious difficulties to be established, due to the most diverse factors (Maasdorp, 1992; Ruiz and Febles, 2006), which makes them vulnerable to the competition with weeds and predators and defoliations during the establishment, as well as grazing and wildlife. In this sense, Ruiz and Febles (2001) and Padilla (2001) indicated that the success of pasture management during establishment is based on the efficient and timely use of the available genetic, environmental and technological factors. If these factors are considered, unproductive vegetation can be replaced by high quality and sustainable vegetation.

Within the Leucaena genus, Sorensson et al. (1993) found differences regarding establishment among species as well as among accessions; for example, Leucaena pallida and its hybrids showed higher vigor than Leucaena leucocephala cv. Cunningham. For such reason, the study of the accessions of a species during the establishment stage, their characterization and evaluation represent a very efficacious way to learn the possible existing differentiation or similarity, and they are, undoubtedly, an efficacious complement among the attributes to be taken into consideration in the selection process.

Due to the above-mentioned reasons, this work was conducted with the objective of learning the performance of the accessions in this stage and select the most outstanding, based on some morphological and yield indicators.

MATERIALS AND METHODS

Location. The study was conducted in areas of the Experimental Station of Pastures and Forages «Indio Hatuey», which is located at 22º 48' and 7'' latitude north and 79º 32' and 2'' longitude west, at an altitude of 19,9 masl, in the Perico municipality, Matanzas province, Cuba (Academia de Ciencias de Cuba, 1989).

Climate characteristics. The performance of the most important climatic variables (table 1) was taken from the monthly records of the meteorological station located in areas of the Institution.

Soil characteristics. The trial was conducted on a plain topography soil, with a slope from 0,5 to 1,0% and classified by Hernández et al. (2003) as lixiviated Ferralitic Red, hydrated ferruginous nodular humic, of rapid desiccation and deep on limestone. This type is equivalent to the Ferrosol group, in the classification system of FAO-UNESCO (Alonso, 2003). The average depth to the limestone is 150 cm. The results of the chemical composition of the soil are shown in table 2.

According to such indicators, the soil of this area tends to be slightly acid, while the organic matter content is high and higher than the report made by Hernández (2000). The total nitrogen content is considered moderate, it shows low available phosphorus values and the exchangeable bases (K, Ca, Mg) show values from moderate to high. According to these characteristics the soil can be considered of moderate fertility.

It shows low apparent density, high total porosity and moderate granular structure, conditions that favor good root development, aeration and water movement. Water retention is low, which can stress the problems derived from seasonal drought (Hernández et al., 2003).

Plant material used. From the 180 accessions existing in the Leucaena spp. collection that are preserved in the germplasm bank of the Institution, 23 were taken (table 3), representative of the population (four plants were used from each one), which were previously evaluated under nursery conditions (Wencomo and Ortiz, 2010).

Experimental procedure. Before making the transplant, weeds were eliminated and the area was maintained clean throughout the establishment time. In the experimental period neither irrigation nor fertilization was used. For the soil preparation the conventional method was used (plough, harrow, cross, harrow and furrow opening), taking into consideration soil type, preceding crop and degree of weed infestation. This trial began when the seedlings reached approximately between 30 and 45 cm (three months old), with healthy appearance. In September four seedlings from each accession were transplanted to the field, in rows separated by 6 m and a space of 3 m between plants. The experimental period lasted 24 months.

Plant height was measured from the moment of transplant, with a ruler graduated in centimeters, which position was perpendicular and always in contact with the soil. The number of branches was also counted and the stem diameter was measured with a caliper. All these measurements were performed monthly on the four transplanted plants, until they were considered established.

The selected accessions should fulfill two or more evaluation criteria, in a period no longer than 14 months, according to the selection criteria established by Seguí et al. (2002):

• Height from 1,50 to 2 m.

• Number of branches higher than 10.

• Stem diameter between 5 and 8 cm.

• Edible biomass yield 0,75 kg DM/plant or more.

Likewise, yield in the establishment cutting was determined; for that 200 g-samples of green forage were extracted and their DM content was calculated.

Statistical processing. Through the main component analysis (MCA) (Morrison, 1967), the measurements performed during the evaluation period (24 months) were processed. As analysis criterion those main components that showed proper values higher than 1 and sum or preponderance factors higher than 0,70 were taken. Likewise, the cluster analysis was applied for the grouping and selection of the accessions using as similarity index the Euclidian distance, from the results of the MCA (Torres et al., 2006), and the mean and standard deviation stadigraphs were obtained for the variables analyzed in this stage.

The results of the indicators after 14 months were subject to an ANOVA according to lineal model of simple classification, and the means were compared through Duncan's test for 5% significance, after verifying that they fulfilled the normal distribution and variance homogeneity adjustment. All the analysis were made by means of the statistical program SPSS® version 11.5 for Microsoft® Windows® (Visuata, 1998).

RESULTS AND DISCUSSION

Table 4 shows the performance of the accessions regarding the evaluated indicators, and the time each one took to reach 1,50 m of height. It was observed that some accessions could be exploited 12 months after transplanted, as in the case of L. leucocephala CIAT-17480, the first to reach such height with only seven months, and by the end of the stage its height was 3,65 m and had an edible biomass yield of 0,82 kg DM/plant.

Although the first seven accessions did not show significant differences with regards to the commercial varieties L. leucocephala cv. Cunningham, cv. Peru and cv. CNIA-250 in terms of height, diameter and number of branches, it is valid to state that the values were numerically higher in some cases, which can be considered encouraging in the selection process. In the case of CNIA-250 the results coincide with the ones obtained by Hernández and Seguí (1998) under nursery conditions, and those obtained by Machado and Núñez (1994) and Wencomo et al. (2001) when evaluating it in the establishment stage, where it also showed a similar performance.

Likewise, in most cases the plants that showed the highest height coincided with the ones with the highest number of branches. This indicates that in these accessions a higher production or biomass availability can be obtained, which is very important for forage production and, thus, for animal feeding; similar results were reported by Dávila and Urbano (1996) in 13 cultivars of L. leucocephala, in which the lowest height values coincided with the lowest ones in diameter, number of branches and average dry matter yield.

Similarly, it could be observed that although there were no significant differences for a large group of accessions in terms of the number of branches, L. leucocephala CIAT-17480 and CIAT-7988 were the most outstanding in this indicator (47 and 44, respectively), followed by L. leucocephala CIAT-751 and CIAT-9438 (42 and 41 for each one). More growths were found in the highest and most vigorous plants.

Establishment constitutes a highly important stage in the promotion of the pastureland and is one of the most difficult periods, because in this stage it is essential to combine, favorably, the conditions inherent to soil and climate, phytotechnical factors and variety characteristics. Most tree legumes grow slowly during the seedling phase, which makes them vulnerable to weed competition and predators and to defoliations during establishment (Ruiz and Febles, 2006), as well as to grazing and wildlife.

This slow initial growth can be related to the little amount of leaf area and also to the growth dynamics and leaf expansion, according to criteria expressed by Díaz (2006). In this sense, the known studies are related to pastures, but according to Anon (2002), the same occurs in shrubby and tree species. Likewise, the problem of growth is related to biomass partition with certain priority during the first weeks towards the root system, which was confirmed by Shelton (2000), who stated that this organ in trees has a high component of permanent structural roots, as well as a system of rootlets, which are responsible for water and nutrient assimilation. A high proportion of the assimilated substances are transferred to the non productive structural part of the tree root.

It must be said that according to Bowen (1985), the roots are also related to the slow growth of the aerial system of plants, because the root system uses most photosynthates for its growth in this initial stage. Root systems have a high proportion of permanent structural roots, as well as a matrix of fine roots responsible for the absorption of nutrients and water. In trees, in general, there is a density of root length that varies between 0,8 and 0,7 cm/cm³, which is much lower than in herbaceous plants (L. leucocephala, between 0,5 and 2 cm³), for which the access to less mobile nutrients become difficult, because the concentration of roots is found at a soil depth of 15-30 cm. Similar considerations were made by Ruiz and Febles (2006).

The slow initial growth in the plants from the accessions of this genus is likely to be specific and the accession, in spite of the existing differences, does not seem to play a decisive role when obtaining a material with much faster establishment, which coincides with the observations made by Sierra (cited by Ruiz and Febles, 1987), who determined an average height of 120 cm in the first 150 days in 90 L. leucocephala varieties. The slowness in this species in its first stages was also indicated by Harding (1972) and Cooksley (1974), and constitutes one of the most adverse limitations in Cuba for its establishment; according to the observations, everything seems to indicate that this is similarly revealed for the accessions of other Leucaena species.

In the main component analysis only one component was obtained, which accounted for 87,94% of the total variance (table 5). In this component all the indicators contributed to express the extracted variance. With this analysis the close relation among the indicators taken into consideration was corroborated.

The variability shown through the indicators can be due to the high relation that existed among them in the analyzed stage, aspect that allows the grouping of the accessions and their later selection regarding the indicators. The high variance percentage explained by that component suggests that it contains indicators that can discriminate well the studied accessions. For such reasons, it could be said that variability was related to the contrast in the performance of these species and accessions, supported by the existing differentiation among the morphological factors that characterize them.

Similar results in terms of variation were obtained by Machado and Núñez (1994), when evaluating eight L. leucocephala accessions on moderate fertility soils, who found a cumulative variance of 81,7% in the first two components, using the same indicators of this study; as well as in studies conducted by Machado (2006) on the establishment of this species on hydromorphic soils of the Ciénaga de Zapata swamp.

This could indicate that, independently from the existing edaphoclimatic conditions during this stage (tables 1 and 2), the populations, and particularly the accessions of the species from the Leucaena genus, could express a remarkable variation among individuals for some indicators and be grouped regarding those variables, which can represent a positive element in the characterization and selection work. This could have been influenced by the interspecific and intraspecific variability of the sample that was formed by several species with their respective accessions, which are remarkably differentiated from the morphological point of view.

Likewise, although in the establishment of trees and shrubs, as in the establishment of other species, a group of indicators must be considered, which relate the concepts of growth and development, emphasis must be also made on the biological characteristics of the species, so that it allows to establish the foundations on which future evaluation and characterization works must be supported.

In correspondence with the high value reached by the cumulative variance and the proper CP₁ value, it is possible to assume that the phenotypical variability was propitious enough for all these indicators to be included in the cluster analysis, and thus determine the differentiation or similarity among the species and accessions.

The cluster analysis based on the results of the MCA during this stage, allowed the formation of three groups. The accessions belonging to each of them are shown in table 6, as well as the mean and standard deviation of each of the groups formed.

According to the results, it can be deduced that the accessions belonging to group I were the highest, most branched and highest yield plants. It is valid to emphasize that the accessions in group I in this stage were the same that stood out under nursery conditions (Wencomo and Ortiz, 2010), for which it could be said that such stage should be considered for the pre-selection of accessions with favorable characteristics, although they should be confirmed in later stages.

These results showed that in the populations of species from this genus individuals can be found capable of showing a similar performance on such soils as the one studied; this could be associated to the possibility of the individual genome to respond favorably to the surrounding environment (Hidalgo, 2003). A similar pattern to that of the outstanding accessions of L. leucocephala was observed by Machado (2006) in L. leucocephala cv. Cunningham, CIAT-482, PI-14, cv. Mexico and CNIA-250, with excellent adaptability characteristics, which confirms the above-mentioned assertions.

In general, it was evident that the establishment dynamics of the plants in the species from this genus showed differences in its performance and among accessions; for such reason, it should not be statically and arbitrarily analyzed, but rather taking into consideration different biotic as well as abiotic factors.

During this evaluation stage all the accessions fulfilled the predetermined selection criteria, although not at the same time, which could have been related to the genotypical characteristics of the plant, the utilization capacity of the nutrients present in the soil or the efficiency with which they were used by the plants.

Another element to be considered is that related to soil, which was not fertilized and it could have affected the growth and development of plants; although it is classified as a moderate fertility soil (Hernández, 2000). An additional factor, related to a higher or lesser extent to the above-mentioned ones as likely to having influenced the results, could be the lack of soil humidity, because of the rainfall deficit during the dry season, which could affect the young growing plant. Similar results were reported in the research conducted by Toral (2005) when evaluating promising tree germplasm for agroforestry systems.

Likewise, this stage allowed to know the establishment of the different accessions under natural conditions, which differed from the nursery stage where semi-controlled conditions for seedling development were guaranteed, mainly the supply of sufficient and stable humidity. Regarding that and the predetermined selection criteria, L. leucocephala cv. Cunningham, cv. Peru, CIAT-9119, CIAT-9438, CIAT-751, CIAT-7988, CIAT-7384, CIAT-7929, CIAT-17480, cv. Ipil-pil and cv. CNIA-250; L. lanceolata CIAT-17255 and CIAT-17501; and L. diversifolia CIAT-17270 stood out. The presence of the three last accessions in the same group as those of the species L. leucocephala indicates that they show very similar performances regarding the evaluated indicators.

According to the results, total variability was concluded to be high (87,94%), which determined a remarkable differentiation among the accessions and particularly for L. leucocephala. The morphological indicators contributed in the later grouping and selection of the most outstanding accessions. There were intraspecific and interspecific differences in the evaluated material in the establishment. The accessions that showed the best performance were: L. leucocephala, CIAT-9119, CIAT-9438, CIAT-751, CIAT-7988, CIAT-7384, CIAT-7929 and CIAT-17480; L. lanceolata CIAT-17255 and CIAT-17501; and L. diversifolia CIAT-17270, in addition to the commercial varieties L. leucocephala cv. Cunningham, cv. Peru, cv. CNIA-250 and cv. Ipil-pil. The selection of the 11 accessions of L. leucocephala, two of L. lanceolata and one of L. diversifolia, represents 60,86% of the total evaluated material, results that are considered acceptable in this type of works. These accessions showed higher values of height, number of branches, stem diameter and yield than the comparison patterns.

For such reason, they are recommended to be included in other studies for the evaluation of the seed production potential (to ensure the development of new areas where silvopastoral systems are used) and the determination of their specific characteristics, as well as all those aspects that are involved in the technological chain of production and quality maintenance.

In addition, the factors related to growth and development must be considered, such as: photosynthetic indicators, respiration, hormonal functioning, leaf area, soil and climate, which allow to complete the studies about the less studied species in this genus.